(1) Field of the Invention
The present invention relates to an emission cleaning installation for cleaning and eliminating emissions, and to an emission cleaning method which uses this emission cleaning installation, and more particular to an emission cleaning installation which can be fitted into existing large-scale incineration furnaces and is able to oxidatively break down environmental pollutants which are contained in the emissions expelled from an incineration furnace and of which dioxins, dibenzofurans, coplanar PCBs, nitrogen oxides (NOx) and the like are representative examples, by the photocatalytic action of a photocatalyst, without control of the emission temperature, and still more particular to an emission cleaning method which uses this emission cleaning installation.
(2) Background of the Related Art
Hitherto, emission cleaning installations which involve cleaning the emissions expelled from incineration furnaces have been proposed as follows:
1. A Cleaning installation whereby the emission supply duct is provided with electrostatic separators or bag filters or cyclones and the like, in order to physically eliminate dioxins from the emissions;
2. A Cleaning installation which is filled with an adsorption agent comprising activated carbons, activated charcoals and the like, in order to eliminate by adsorption environmental pollutants of which the dioxins contained in the emissions are representative;
3. A Device which mixes photocatalysts for breaking down environmental pollutants in the emissions by oxidation, by means of the photocatalytic effect of the photocatalyst with the emissions, and introduces them into an emission decomposition tower, and which recovers the photocatalyst by means of dust separators downstream of the emission decomposition tower after the photocatalyst has been photoexcited by means of ultraviolet light emitted from a low-pressure mercury lamp, thus revealing its photocatalytic effect (patent application JP-H05-285342).
However, the emission cleaning installation which is described in patent application JP-H05-285342 is an installation which mixes the photocatalyst into the emissions, and if a large amount of photocatalysts is mixed into the emissions, the transmission through the emissions deteriorates (because the light is reflected, and consequently the light transmission deteriorates). Although it is possible for exciting light which is radiated from the light source to be radiated to a sufficient extent with respect to the photocatalyst situated relatively close to the light source, and therefore the photocatalyst can be photoexcited, thus revealing the photocatalytic action (=photocatalytic function), the exciting light (which is emitted from the light source) cannot be radiated to a sufficient extent with respect to the photocatalyst situated at a distance from the light source. Therefore, because the photocatalyst cannot be sufficiently photoexcited, the photocatalytic function of these photocatalysts cannot be sufficiently displayed and, overall, it is known that there are problems with the efficiency of the emission cleaning method brought about by the photocatalytic action (=photocatalytic function) of the photocatalyst being reduced considerably.
There were also further problems relating to the cleaning installation overall becoming complicated and therefore more expensive, since the photocatalyst had to be separated back out of the decomposition gas after treatment, for example by means of separators and the like.
On the other hand, there are elimination problems with devices provided with electrostatic separators or bag filters or cyclones and the like and there are also problems with eliminating and recovering dioxins and the like in the emissions using such devices. Specifically, of the dioxins contained in the emissions, although it is possible to eliminate the dioxins contained in fly ash, together with dust materials, the dioxins adhering to very fine fly ash, low-boiling, gaseous dioxins and the like cannot be eliminated.
Furthermore, since the emissions expelled from incineration furnaces are generally at elevated temperatures, a control unit is required if such environmental pollutants are eliminated and recovered, for example by means of separators, in order to provide rapid, considerable cooling of hot emissions by means of cooling devices and the like before they are fed to the separator. This led to problems in terms of the emission cleaning installation overall becoming complicated and more expensive. Moreover, similar problems are encountered with emission cleaning installations which use bag filters or cyclones.
On the other hand, it has been proposed to initiate decomposition processes by oxidation using a metallic catalyst made from titanium, vanadium, platinum and the like as an additional agent. However, since in this decomposition process by oxidation carried out by the metallic catalyst, the effective temperature of the atmosphere is in the region of 230xc2x0 C., and also the temperature range which will be effective is narrow, it is necessary for the emissions to be quickly and considerably cooled by means of a cooling device or the like before they are fed to the separator or bag filter or the cyclone, yet at the same time it is necessary for the cooled emissions to be heated and for their temperature to rise again; this makes temperature control of the emissions very troublesome and laborious.
Furthermore, in elimination methods carried out by absorption agents comprising the abovementioned activated carbons or activated charcoals, although in theory it is possible for the low-boiling, gaseous dioxins to be eliminated, it is also necessary for the used waste adsorption agent which has absorbed dioxins to be fed for secondary treatment. Additionally, because the emission temperature is in the region of greater than 150xc2x0 C., dioxins which have been absorbed with great difficulty become separated from the adsorption agent and are then deposited, or because the adsorption capacity of activated carbons falls, and then the desired elimination by adsorption can no longer be achieved, or because the emission temperature generally fluctuates readily and constantly, various problems are always encountered, involving the dioxins which have been adsorbed at high temperature becoming separated and then dispersed in the emissions once again, etc.
The present invention involves providing an emission cleaning installation by means of which environmental pollutants in the emissions, which have been expelled from the incineration furnace and of which dioxins, dibenzofurans, coplanar PCBs and the like are representative examples, can be broken down by oxidation by the photocatalytic action of the photocatalyst, and by means of which they can be cleaned and treated until they can be discharged to atmosphere.
The invention also involves providing an emission cleaning installation with which emissions which have been expelled from the incineration furnace can be cleaned and treated without temperature control and which, if necessary, are easy to retrofit in existing large-scale incineration furnaces.
The invention furthermore involves providing an emission cleaning installation which is designed in such a way that, in order for the photocatalytic action of the photocatalyst to be displayed to a sufficient extent, the light source is a combination of a disinfecting lamp, which has its maximum wavelength in the vicinity of 254 nm, and a black light lamp, which has its maximum wavelength in the vicinity of 380 nm, and that the abovementioned light source can radiate sufficient exciting light onto all the photocatalysts. This can be achieved by the fact that the surface of the photocatalyst is excited by ultraviolet light which is radiated from the disinfecting lamp, while the ultraviolet light which is radiated out of the black light lamp is allowed to pass through the photocatalyst and penetrate into the interior of the photocatalyst container.
Furthermore, the invention involves providing an emission cleaning installation which uses photocatalyst pellets which are in the form of porous bodies and are formed by coating the surface of the porous metal body with a titanium oxide coating in the anatase form as its crystalline form, in order to increase the specific surface area of the photocatalyst pellets.
Furthermore, the invention involves providing an emission cleaning installation which uses photocatalyst pellets which are formed by coating the surface of the porous ceramic support with a titanium oxide coating in the anatase form as its crystalline form, in order to increase the specific surface area of the photocatalyst pellets. Examples of porous ceramic supports which may be mentioned are activated carbon, activated alumina, silica gel, porous glass and the like.
The invention furthermore involves providing an emission cleaning installation which uses photocatalyst pellets which are formed by coating one of the surfaces with woven fabric which weaves in heat-resistant fibres, nonwoven fabric, knitted fabrics or any other type of fibrous structure with a titanium oxide coating in the anatase form as its crystalline form.
The invention also involves providing an emission cleaning installation which uses photocatalyst pellets, consisting in the surface of the titanium oxide coating being coated again with a type of metal coating which is selected from groups consisting of platinum, rhodium, ruthenium, palladium, iron, silver, copper and zinc.
Furthermore, the invention also involves providing an emission cleaning method which is characterized in that the photocatalyst pellets are accommodated in the interior of an ultraviolet light permeable cylinder body, and an emission cleaning installation, which is provided with a light source which radiates the light for exciting the above-described photocatalyst pellets on the outer side of the corresponding cylinder body, continuously adjoins the emission supply duct of the incineration furnace, whereby the emissions expelled from the incineration furnace are introduced at a constant, high temperature into the interior of the abovementioned cylinder body and come into contact with the above-described photocatalyst pellets leading to environmental pollutants in the emissions being broken down by oxidation.
Furthermore, the invention also involves providing an emission cleaning method which is characterized in that the emission cleaning installation is provided with a housing section having an ultraviolet light permeable cylinder body, with photocatalyst pellets, which are accommodated in its interior and come into contact with the emissions expelled from the incineration furnace, and with a light source, which is fitted in the interior of the abovementioned cylinder body and photoexcites the abovementioned photocatalyst pellets. Said emission cleaning installation, comprises a plurality of spaces which alternately communicate with one another on the upper cover side and baseplate side or on opposite side wall sides continuously adjoining the emission supply duct, whereby the abovementioned emissions are introduced into the abovementioned spaces at a constant, high temperature and then come into contact with the abovementioned photocatalyst pellets leading to environmental pollutants which are contained in the emissions being broken down and eliminated.
Furthermore, the invention also involves providing an emission cleaning method which is characterized in that the cleaning installation is provided with a filter container, the interior of which is filled with filtration materials, with a photocatalyst container, which continuously adjoins the corresponding filter container in a freely removable manner via or without the heat-resistant component and the interior of which is filled with photocatalyst pellets, and with a component for expelling emissions, which continuously adjoins the corresponding photocatalyst container via or without a heat-resistant component. The abovementioned photocatalyst container is designed in such a way that it contains a plurality of cylindrical housings, which pass through the interior of the corresponding photocatalyst container and allow ultraviolet light to pass through, and a light source, which is fitted in each housing and photoexcites the abovementioned photocatalyst pellets, and continuously adjoins the emission supply duct of the incineration furnace with a connecting component between them. The emissions are introduced into the interior of the abovementioned photocatalyst container at a constant, high temperature and come into contact with the abovementioned photocatalyst pellets leading to environmental pollutants which are contained in the emissions expelled from the abovementioned incineration furnace being broken down and eliminated.
Accordingly, an object of the present invention is to provide an emission cleaning installation and an emission cleaning method, in particular an emission cleaning installation which can readily be continuously connected even to existing large-scale incineration furnaces, and which is able to break down and eliminate by oxidation the components such as, for example, dioxins, dibenzofurans, coplanar PCBs, nitrogen oxides (NOx) and the like which are contained in the emissions without temperature control of the emission temperature, by photocatalytic action, and providing a method for cleaning and eliminating emissions which uses the abovementioned emission cleaning installation.
Another important object of the present invention is to provide an emission cleaning installation having an ultraviolet light permeable cylinder body, which passes through ultraviolet light and through which the emissions supplied from the abovementioned incineration furnace pass. Said cylinder body has photocatalyst pellets which are accommodated in the interior of the abovementioned cylinder body and come into contact with the abovementioned emissions, and a light source which is arranged on the outer side of the abovementioned cylinder body and radiates exciting light for exciting the abovementioned photocatalyst pellets. Said installation can be continuously connected to the emission supply duct (flue duct) of the existing large-scale incineration furnace.
A further object of the present invention is to provide an emission cleaning installation which has a plurality of spaces which alternately communicate with one another on the upper cover side and the baseplate side or on opposite side wall sides, each space being designed in such a way that it is provided with a housing. Said housing has an ultraviolet light permeable cylinder body, with photocatalyst pellets, which are accommodated in the abovementioned spaces and with which the emissions expelled from the abovementioned incineration furnace come into contact, and a light source, which is provided in the interior of the abovementioned cylinder body and radiates the exciting light which excites the abovementioned photocatalyst pellets. Said installation can be continuously connected to the emission supply duct of the existing large-scale incineration furnace.
Yet another object of the invention is to provide an emission cleaning installation which continuously adjoins the emission supply duct of the incineration furnace, with a connecting component between them, and is provided with a rectangular filter container, the interior of which is filled with filtration materials, with a photocatalyst container, which continuously adjoins the abovementioned filter container in a freely removable manner via or without a heat-resistant component and the interior of which is filled with photocatalyst pellets, and with a component for expelling emissions, which continuously adjoins the abovementioned photocatalyst container via or without a heat-resistant component. The abovementioned photocatalyst container is provided with a plurality of cylindrical housings, which allow ultraviolet light to pass through the interior of the corresponding photocatalyst container, and with a light source, which is fitted in each housing and radiates light for exciting the abovementioned photocatalyst pellets. In particular, in the exemplary embodiment which has just been described, the abovementioned filtration materials are designed in such a way that.they contain either spherical ceramics or silica gel with an alkali-treated diameter of from 5-25 mm. A removal hole for the photocatalyst is formed at the bottom end section of the side wall of the photocatalyst container, and the base surface is designed to slope from its central section downwards towards the abovementioned removal hole, in the form of a gable or hipped roof.
Furthermore, in accomplishing each of the abovementioned objects in the preferred exemplary embodiments, the photocatalyst pellets used are such that either the surface of porous metal supports or the surface of porous ceramics or the surface of woven fabric which weaves in heat-resistant fibres, nonwoven, knitted fabrics, or the surface of any other type of fibrous structures are coated with a titanium oxide coating of the anatase form as the crystalline form.
Furthermore, in accomplishing the objects of the present invention in the preferred exemplary embodiments described above, it is also possible to use photocatalyst pellets which are such that the surface of the titanium oxide coating is coated again with a type of metal coating which is selected from groups consisting of platinum, rhodium, ruthenium, palladium, iron, silver, copper and zinc.
Furthermore, in accomplishing the objects of the present invention in the preferred exemplary embodiments described above, the light source used comprises a combination of a disinfecting lamp, which has its maximum wavelength in the vicinity of 254 nm and radiates ultraviolet light, and a black light lamp, which has its maximum wavelength in the vicinity of 380 nm and radiates ultraviolet light, and consequently, the exciting light can be radiated to a sufficient extent onto all the photocatalyst pellets.